To provide a millimeter wave modulator which controls a bias current made to flow into a detection diode and has stable and excellent switching properties.
In the millimeter wave modulator (ASK modulator M1), a diode (SBD) 36 having a millimeter wave signal detecting action to a millimeter wave signal is connected in series in the middle of a choke type bias supply line (choke inductor 35) constituted by alternately forming a wide line and a narrow line formed on a substrate, and a switch 37, a constant current circuit element (CRD 33), and a power source (constant voltage source 32) are connected in series to the choke type bias supply line (choke inductor 35). A bias current made to flow through a bias circuit C1 to the diode 36 can be controlled to a constant current regardless of variation of detection current, thereby stabilizing the operation of the diode 36, so that a desired millimeter wave modulation output can be stably obtained.
HIRAMATSU NOBUKI
KISHIDA YUJI
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